Question : Page life expectancy

Sometimes the Page life expectancy counter of our server is very low. We have many fluctuations. Is this normal?
What can be the reason why there are so much fall backs below the advised 300? We have no memory problem, and also only missing indexes with to much included columns.
This is an example of the fluctuations during a few hours:
YYYY-MM-DD HH:MM cntPage
---------------- -----------
2009-12-16 11:35 374
2009-12-16 11:30 175
2009-12-16 11:25 9
2009-12-16 11:20 277
2009-12-16 11:15 624
2009-12-16 11:10 538
2009-12-16 11:05 238
2009-12-16 11:00 8
2009-12-16 10:55 930
2009-12-16 10:50 659
2009-12-16 10:45 358
2009-12-16 10:40 182
2009-12-16 10:35 198
2009-12-16 10:30 10
2009-12-16 10:25 572
2009-12-16 10:20 272
2009-12-16 10:15 246
2009-12-16 10:10 172
2009-12-16 10:05 8
2009-12-16 10:00 274

Answer : Page life expectancy

Yes you are right about 8KB page and the math. Which counter were you showing the target and total from? If you are showing the SQLServer Memory Target Server Memory and Total Server Memory that is in KB... http://msdn.microsoft.com/en-us/library/ms190924.aspx

What counter were you showing referring to the Target and Total???

Also looking at your Private Bytes and Working set and doing the math it seems to line up with the analysis in terms of KB.

Again, can you please tell me how large your databases are and what kind of activity you are experiencing?  The odd thing here is that you just don't have a lot of memory that I can see in use but your available memory isn't so high. I wonder how this will look after a reboot.